The scroll exceeds the visible area when using the auto-fill.

Steps to reproduce:

- Set the VisibleSize to (10 ,10)

- Drag the autofill icon down

When attaching to the CellPropertyChanged event and trying to modify the cell an exception is thrown:

if firstly detached from the event and then modify the cell the exception is: 
System.InvalidOperationException: 'Collection was modified; enumeration operation may not execute.' 

else:
System.StackOverflowException: 'Exception of type 'System.StackOverflowException' was thrown.'

Cell Values disappearing when RadWindow is dragged to a second Monitor.

Workaround:

private void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
    this.viewModel.OpenSampleCommand.Execute(null);
    radDocking1.ToolWindowCreated += RadDocking1_ToolWindowCreated;
}

private void RadDocking1_ToolWindowCreated(object sender, Telerik.Windows.Controls.Docking.ElementCreatedEventArgs e)
{
    var window = e.CreatedElement as ToolWindow;
    if (window != null)
    {
        window.WindowStateChanged += Window_WindowStateChanged;

    }
}

private void Window_WindowStateChanged(object sender, EventArgs e)
{
    var window = sender as ToolWindow;

    var spreadsheet = window.ChildrenOfType<RadSpreadsheet>().FirstOrDefault();
    if (spreadsheet != null)
    {
        spreadsheet.InvalidateVisual();
    }
}

Setting up a paper size to A1 and exporting it actually sets the paperSize to 1. Using the same scenario in Excel sets the paperSize to 305.

This leads to inappropriate values when entering the Page Setup options later in Excel.